Lecture Notes: How DNA Results in a Trait

Introduction

• DNA contains genetic information for traits (e.g., eye color).
• Genes code for proteins that are crucial for making pigments like those in eyes.

Protein Synthesis

• Definition: Process by which DNA leads to protein creation.
• Importance of Proteins:
  • Involved in transport, structure, enzyme activity, protection, etc.
  • Essential for life; proteins are constantly produced in cells.

Role of DNA

• DNA is found in the nucleus of cells.
• Some DNA is non-coding or inactive.
• Focus on genes that code for active proteins.

Role of RNA

• RNA is a nucleic acid similar to DNA but with key differences.
• Critical for protein synthesis.

Protein Synthesis Steps

1. Transcription

   • Occurs in the nucleus.
   • DNA is transcribed into mRNA by RNA polymerase.
   • mRNA (messenger RNA) carries a message based on DNA.
   • mRNA undergoes editing before being functional.
   • mRNA exits the nucleus to the cytoplasm.

2. Translation

   • Occurs in the cytoplasm at the ribosome.
   • Ribosomes are made of rRNA (ribosomal RNA).
   • Translation involves reading mRNA to make protein.
   • tRNA (transfer RNA): Carries amino acids, reads mRNA codons in triplet sequences (codons).
   • Each tRNA has an anticodon complementary to the mRNA codon.

Codons and Amino Acids

• Codon: 3-base sequence on mRNA; directs tRNA for corresponding amino acids.
• Example:
  • Codon AUG on mRNA matches tRNA anticodon UAC, carrying methionine.
  • Methionine often starts protein synthesis.
• Codon Chart: Tool to determine which amino acids correspond to mRNA codons.
• Multiple codons can code for the same amino acid (e.g., leucine).
• Stop Codons: Signal end of protein synthesis.

Protein Chain Formation

• Amino acids linked by peptide bonds.
• Sequence based on mRNA coding.
• DNA as the director of protein synthesis with the help of RNA.

Additional Information

• Post-translation protein folding and modification.
• Protein transport varies based on function.

Conclusion

• Protein synthesis is a complex process involving DNA, mRNA, rRNA, and tRNA.
• Stay curious and explore more about these fascinating biological processes.